Resilient hitch for portable measuring devices



'P. 5 REGNA 2,505,205 RESILIENT HITCH FOR PORTABLE MEASURING DEVICESApril25, 1950 Filed Jan. 25, 1945 INVENTOR. PAUL G.REGNA FIG! / TORNEYPatented Apr. 25, 1950 u .lirr ear ENIT oiserc RESILIEN '1 HITCHFORPORTABLE MEASURING DEVICES BauI'GQRegna, St. Louis, M0,, assignor toWagner Electriczflorporationg' St. Ii'ouis, Mo.,. a. corpora-.-

tion' ofD'elaware- Application "January'25 1945; Serial No. 5745543 2'Claims: (Cl. 73-1-128 This invention relates tc'means formaintaining.substantially constant contact pressure betweenithe roadsurface andlaxwheel of a-trailer towed. by another vehicle;Oneparticular application .for' such means is in brake :testingapparatus (sometimes designated 'as'a stopmeter") by. means of which thedistance traveledbyv a vehicle after fulLappli'cation ofthe brakes maybe indicated. One such .prior stopmeter' apparatus is illustratedinMilster et. a1. Patent No.

In sto'pmeters the :tr'ailerwheel whichactuates the indicating.apparatusis equipped with. a pneumatic tire and since the distance.traveled, asindicated-by instrumentsdriven by this wheel; is a. functionof the .number.ofirotations of the wheel, a variation during the .testoi..fthe effective radius of thewheeI (distance from wheel center. topoint .of contact with the road surface and which, dueto deformation ofthe tire bypressures. effective, will be less than other radii along.which. no pressure is applied)v assumed in. fixingthe calibrations ofthe indicating instrument, will.

result in erroneous indications of=the.;actual dis.-

tance. traveled. The. body of. a. vehicle, whose f brakes-are beingtested, is resilientlymountedand.

the rear-bumper of M the. vehicle constitutes. the.

most: convenient point. of attachment of the trailer unit. Consequently,during a test therev maybe variations in. the-vertical positionof thepoint-of attachmentof the trailer wheel frame to the vehicle.

It has heretofore been 'the practiceto apply spri-ng means forproducingscontact pressure ice-.-

tween the trailer wheel andthe roadsurface abovethat-imposed by gravityto assure that the wheel will be maintained in constant engagement withthe road surface;.b'ut-"so'i'farr asr is known, it has. not heretoforebeen. proposed to provide spring means having such characteristics andso.

related to the trailer wheel supporting frame as to maintain constant"contact pressure between the trailer wheel and the roadrand, therefore,

Figure 2 shows an enlarged planview of "a -sec tion of the trailerhitch;

Figure 3 shows an enlarged vertical elevational view, partly in section,to show details of con struction of the trailer hitch; and

Figure 4 is a schematic view of 'a modified'form of the invention.

The achievement of 'the above object is obtained'in the device set-forthin the accompany-'- ingdrawings in which I is a portion-of the'rearbumper of a towing vehicle'to which the -trailer" unit is attached. Thishitch may also be secured toother partsof the towing vehicle. Numeral 2represents generally the trailer hitch having ahousing 3 pivotallysecured thereto and a frame e'in'whichwheel'fi is rotatably mountedon anaxle 6- which is pivoted to the housing 3 by means-- of a spindl'e'orpin 1 to allow the frame 4 and associated wheel 5'to move verticallywith respect to housing 3 and bumper I about! aS an axle. A housing 8 isshown'conveniently mounted on frame 4- and a drive shaft 9 connected topower intake on housing 8, transmits'motion from the" wheel througliaspeed changer l0 associated with the wheel 5 and axle 6 to therebytransmitrotative motionirom the. wheel of the'mechanismcontainedinhousing 8 and record the travel of J wheel 5. The mechanismcontained in housing8 maybe of the type'shown in Milster copending.applications Serial Nos. 568,532, now Patent No. 2,472,541, and 568,533,now Patent No. 2,486,965, filed December 16, 1944. Theoperation of the.mechanism is fully setlforth in the several applications and, therefore,need. not be repeated. herein.

The trailer hitch comprises an appropriate bracket element I! that isattachable to the bumperl orany other part-=of:the towing vehicle. andBrfiXtlll'E-I 2 is secured thereto bymeans of a plurality of .bolts I34The housing 3.has a pair oflugs 14 thereon that are axially disposed andare: bored to receive a pin it suitably secured to fixturel2 andprovided in the lugs or brackets- M; The pin is is secured to thefixture-l'lby screws 11.-

HOLISiIIgBYiS bored as at. l8 to receive a-springls havingarfixture 2!]fitting intothe endof the spring; The" fixture. 20- is suitably boredand countersunk to receive a. flexible bolt or; cable-- 2i that-extendsconcentrically of the compression spring 59 down through the lower endof housing 3 and is there wrapped about a sheave 22. sheave Z2 is flaredand extended, as indicated, between parts 23 and 24 and the cable 2| isreceived in an appropriate slot and socket as more particularly shown inFigure 2. The flared extensions in the sheave are suitably bored toreceive tubular frame elements 4 and secured therein by a plurality ofretaining members 25. The pin 1 is received in flanges 26 and 21integrally associated with said housing and pin 1 is received thereinand held in position by an appropriate retaining member 28. A removableclosure element 29 is provided for the housing 3.

During periods of rest or removal of the trailer unit from the towingvehicle, a knurled pin 30, as shown in Figure 2, is provided to lock'thespring in a fixed position in order to prevent it from being effective.

Stop elements 3! and 32 having lock screws 33 and 35, respectively,threaded into each are intended to engage with abutments 35 and 36 tolimit the side sway of the trailer unit about 15 as an axis. Screws 33and 35 are employable to vary the amount of side sway that would bepermitted in-the trailer unit such-as occurs during the backing of thevehicle. The stops are preferably set to limit the side sway to sevenand one-half degrees from the center or a total swing of fifteen degreesas a maximum and screws 33 and 35 may limit the extent of side sway toany amount desirable as may be determined by the operator.

The modified structure shown in Figure 4 illustrates the frame 4 andwheel in which a lever 3! replaces the sheave structure and the housing3 is schematically illustrated with the spring Ill therein. Theconnecting means in the form of a rigid bolt 38 connects the eye of thelever with element 2i! in order-to apply the action of spring l9 to thetrailer wheel 5. The dotted line illustration of 3 and 5 shows themaximum vertical movement, which is approximately forty-five degrees,that the arm Q and wheel 5 will pivot without materially changing thepressure between wheel 5 and the surface traversed.

. The device maintains a substantially constant pressure between wheel 5and the surface traversed when the frame 4 pivots about spindleregardless of surface undulations and the vertical positioning ormovement of the bumper l of the towing vehicle relative to said surface.The foregoing result is obtained because the effective length of themoment arm about which wheel 5 acts varies as the wheel moves verticallyrelative to spindle i. This change in effective length of the wheelmoment arm is accompanied by corresponding changes in the force exertedby the spring is as it changes length. The rate of bull-clup ofresistance of the spring and the po nt of application of the spring tothe frame are each so chosen as to cause the wheel to engage the road atsubstantially the same pressure under all operative variations in thevertical position of the spindle l. The effective length of the momentarm on which spring I9 acts (see Fi ure 3) remains uniform for allvariations in the vertical position of wheel 5 relative to spindle 1 andbecause the effective moment :arm about which wheel 5 swings, changes inlength and the force exerted by spring i9 correspondingly changes, thepressure exerted by wheel 5 on the surface traversed, therefore, remainssubstantially constant. The device shown in Figure 4 operates in asimilar manner. In the form shown in this figure the effective'length ofthe spring arm will vary sli htly under the operative motions of frame 4on spindle 1 but experience has shown that this variation is notsufficient to impair the accuracy of the measuring device.

From the foregoing it is evident that means has been provided thatmaintains a substantially constant contact pressure between wheel 5 andthe surface traversed and that produces far more accurate results thanwhen adjustments are made manually as in presently known devices.

Having fully described my invention, that which I claim as novel anddesire to protect by Letters Patent of the United States is:

1. In a mechanism for association with a vehicle for driving aninstrument for recording distance, means'securable to a vehicle to betested; a sheave .pivotally mounted in said means; a frame supporting aroad engaging wheel for driving the instrument and secured to saidsheave; a spring; and means connected to said spring and operativelyassociated with said sheave to enable said spring to urge said wheelinto engagement with the road surface, said sheave constituting a leverarm of uniform length on which said spring acts under all operativevariations in the rotative position of said frame about the pivot point,the

distance of the wheel on said frame from the pivot point and the rate ofbuild-up of spring resistance being so chosen as to cause the drivewheel to engage the road at substantially the same pressure under alloperative variations in the vertical position of said sheave.

2. A resilient hitch for a portable measuring device of the type thatmeasures the distance of travel of a vehicle following brakeapplication, comprising a frame, for attachment to the body of a vehicleand movable therewith, a housingpivotally connected to said frame on avertical axis, stop means extending from opposite sides of said frame tolimit the lateral displacement of said housing relative to the line oftravel of the vehicle, resilient means carried by the housing, a wheelframe carrying a road engaging wheel for actuating the measuring device,said frame being pivotally. connected to said housing on a horizontalaxis beneath said resilient means and capable of vertical displacementrelative to the vehicle, a uniform length moment arm comprising a sheaveconnected to said frame, and means extending between said resilientmeans and said moment arm to apply the force of the resilient means tothe wheel frame and thence to the wheel to apply uniform pressure of thewheel to the road surface over which the vehicle moves regardless of thevertical displacement of'the wheel frame relative to the vehicle or thevertical displacement of the vehicle frame relative to its supportingwheels.

" PAUL G. REGNA.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Brunner Feb. 27. 1945

